Tool Deflection Control by a Sensory Spindle Slide for Milling Machine Tools

A conventional spindle slide of a milling center is enhanced to a force "feeling" component for process monitoring and control tasks. The feeling ability is realized by integrating strain gauges in notches machined into the structure. This force sensing allows the identification of the static tool stiffness and enables the online detection of the tool deflection during milling processes. Based on a communication via PROFIBUS between the monitoring system and the machine control, the tool deflection is controlled online in the milling center by adjusting the axis feed. The approach shows considerable improvement regarding surface accuracies. © 2017 The Authors. Published by Elsevier B.V.DFG/CRC/65

Self-adjusting process monitoring system in series production

Modern monitoring systems in machine tools are able to detect process errors promptly. Still, the application of monitoring systems is restricted by the complexity of parameterization for save monitoring. In most cases, only specially trained personnel can handle this job especially for multi-purpose machines. The aim of the research project "Proceed" is to figure out in which extent a self-parameterization and autonomous optimization of monitoring systems in industrial series production can be realized. Therefore, a self-adjusting and self-tuning process monitoring system for series production has been developed. This system is based on multi-criteria sensor signal evaluation and is able to assess its monitoring quality quantitatively. For this purpose, the complete process chain of parameterization has been automated. For series production it is assumed, that the first process is not defective. So, process sensitive features are identified by a correlation analysis with a reference signal. The reference signal is selected through an analysis of the process state by an expert system. To assess the monitoring quality resulting from automatic parameterization, normed specific values were used. These values describe the monitoring quality with the help of the distance between a feature and its threshold normed to signal amplitude and noise. A second indicator is the reaction of the monitoring system to a synthetic error added to signal a sequence. Thus it is possible to estimate monitoring quality corresponding to automatic parameterization. The validation is carried out by a comparison between the result of the assessment and the reaction ability of the monitoring system to real process errors from milling, drilling and turning processes.DFG/DE 447/96–

Design and Optimisation of an Electromagnetic Linear Guide for Ultra-Precision High Performance Cutting

Ultra-precision machining is rarely used in the production industry due to high costs as a consequence of disproportionally long primary and secondary processing times. In this context, the implementation of innovative machine technologies presents a suitable approach to increase productivity and reduce manufacturing costs. This paper introduces the implementation of an electromagnetic linear guide within a two-axis positioning stage for ultra-precision and micro machining. Using analytical models and FEM simulations, an optimised design for the guide's structure and magnet configuration is developed with regard to the intended application in ultra-precision high performance cutting. The new guide system provides frictionless operation for rapid and precise feed movements. Stiffness and damping of the electromagnetic guide can be adjusted to current process requirements. Fine positioning of the levitating carriage within the air gap enables an increase of the overall position accuracy.DFG/FOR/184

Analysis of an Ultra-precision Positioning System and Parametrization of Its Structural Model for Error Compensation

Conventional compensation of position errors of machine tools relies only on measured values. Due to this principle it is not always possible to compensate the errors in time, especially dynamic ones. Moreover, the relevant control variables cannot always be measured directly. Thus, this approach proves to be insufficient for high precision applications. In this context, a model-based error prediction allows for minimal position errors. However, ultra-precision applications set high demands for the models' accuracy. This paper presents the design of an accurate and real time-capable structural model of an ultra-precision positioning system. The modeling method for the developed ultra-precision demonstrator is shown and the initial parameter identification is presented. © 2017 The Authors. Published by Elsevier B.V.DFG/FOR/184

Electromagnetic levitation guide for use in ultra-precision milling centres

Today's machine tools for ultra-precision machining are generally characterised by low productivity. Above all, practical cutting parameters are limited due to uncontrollable disturbance forces. Therefore, it is necessary to pursue the qualification of new technologies to overcome current limitations in productivity. In this paper, an approach for the design of a novel electromagnetic levitation guide for use in ultra-precision milling centres is presented. Design and arrangement of the magnetic guide's components are considered with regard to requirements and design principles of precision machines. Deterministic methods are utilised throughout the engineering process to ensure high stiffness and high dynamics. As a result, a concept for the electromagnetic ultra-precision linear guide is derived.DFG/FOR/184

Conceptual Design for Electromagnetic Guided Rotary Table in Machine Tools

Difficult-to-machine materials are still challenging the production industry. Examples are highly complex components of aircraft engines. Alongside innovative processes, also improved machine tool components are helping to comply with the demands of this task. This paper presents a design approach of a rotary table with an active magnetic bearing. Opportunities in machining through employing magnetic guides are presented and discussed in the beginning. In the following, a workflow for the magnetic bearing design in swivel rotary tables is proposed. The mentioned steps are executed based on a presently under design rotary table

Sensor integration for a hydraulic clamping system

Failures in workpiece positioning influence the machining conditions and outcome of machine tools directly. Hence, the monitoring by a sensor integrated clamping system to avoid rejects is subject of the presented work. The overall aim is to integrate sensory capabilities in a hydraulic clamping system typically used in series production within a joint research project. This paper gives a general survey of the targeted application and focuses on the sensor integration. It shows the qualification of strain gauges for indirect measurement of oil pressure in the hydraulic clamping element and the potential use of the same strain gauges to measure further monitoring objectives

Production Monitoring based on Sensing Clamping Elements

Clamping errors in workpiece positioning decrease the production outcome of machine tools by causing rejects. An automated monitoring of these failures does not take place in practice, due to limited installation space for the sensor integration, especially in series production. Within the Collaborative Research Centre 653, the IFW develops and investigates a condition and process monitoring system based on sensing clamping elements in close cooperation with two industrial partners, the companies Roemheld GmbH (clamping technology manufacturer) and ReiKam GmbH (fixture construction service provider). It consists of hydraulic clamping elements with integrated sensors, decentral electronics for signal preprocessing, bus communication and a central processing unit. Measureable quantities are hydraulic pressure, the clamping stroke and the process forces. This article describes the prototypical realization and shows its usability in condition and process monitoring. Experimental results from measurements during milling operations and the comparison with a dynamometer demonstrate the performance of the sensory clamping system